U.S. patent number 4,581,707 [Application Number 06/346,068] was granted by the patent office on 1986-04-08 for microprocessor controlled valve flow indicators.
This patent grant is currently assigned to John Millar (U.K.) Limited. Invention is credited to John Millar.
United States Patent |
4,581,707 |
Millar |
April 8, 1986 |
Microprocessor controlled valve flow indicators
Abstract
A device for ascertaining flow rate through one or more valves
and/or pumps simultaneously. A transducer (T.10) is connected to
the valve actuator member and displaceable or rotatable therewith
and produces an output determined by the valve position. The output
of the transducer is supplied to an electronic processing mean (13)
programmed to calculate the flow rate from data relating to the
flow characteristics of the or each valve and data relating to the
flow characteristics of the fluid concerned and the temperature and
pressure and to display the calculated flow rate or utilize the
calculated flow rate to control the valve position to regulate the
flow rate.
Inventors: |
Millar; John (Hoylake,
GB) |
Assignee: |
John Millar (U.K.) Limited
(Hoylake, GB)
|
Family
ID: |
10513733 |
Appl.
No.: |
06/346,068 |
Filed: |
January 22, 1982 |
PCT
Filed: |
May 22, 1981 |
PCT No.: |
PCT/GB81/00092 |
371
Date: |
January 22, 1982 |
102(e)
Date: |
January 22, 1982 |
PCT
Pub. No.: |
WO81/03542 |
PCT
Pub. Date: |
December 10, 1981 |
Foreign Application Priority Data
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May 30, 1980 [GB] |
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8017809 |
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Current U.S.
Class: |
702/47;
73/861 |
Current CPC
Class: |
G01F
1/00 (20130101) |
Current International
Class: |
G01F
1/00 (20060101); G06F 17/40 (20060101); G01F
001/00 () |
Field of
Search: |
;364/509,510 ;137/551
;251/129 ;73/168,198,861 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1476831 |
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Jun 1977 |
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GB |
|
2026704 |
|
Feb 1980 |
|
GB |
|
Primary Examiner: Krass; Errol A.
Assistant Examiner: Cosimano; Edward R.
Attorney, Agent or Firm: Gottlieb, Rackman & Reisman
Claims
I claim:
1. A device for monitoring the flow rate through at least one valve
to enable each said valve to be converted effectively into a flow
meter, said device comprising a transducer connected to each said
valve for providing a first signal representative of the position
of the valve member of each said valve, electronic processing means
which receives said first signal and having means enabling input of
further signals representing static initial conditions and variable
operating conditions influencing the flow rate, wherein said
electronic processing means includes means enabling storage of data
relating to the flow characteristic curves of a plurality of
different types of valves, whereby said electronic processing means
calculates the flow rate through each said valve from (a) said
first signal, (b) the flow characteristics of said valve and (c)
said further signals, said device further comprising display means
connected to the output of said electronic processing means for
displaying said calculated flow rate.
2. A device for monitoring the flow rate through at least one valve
to enable each said valve to be converted effectively into a flow
meter, said device comprising a transducer connected to each said
valve for providing a first signal representative of the position
of the valve member of each said valve, a electronic processing
means which receives said first signal and having means enabling
input of further signals representing static initial conditions and
variable operating conditions influencing the flow rate, wherein
said electronic processing means includes means enabling storage of
data relating to the flow characteristic curves of a plurality of
different types of valves, whereby said electronic processing means
calculates the flow rate through each said valve from (a) said
first signal, (b) the flow characteristics of said valve and (c)
said further signals, said device further comprising control means
connected to the output of said electronic processing means for
adjusting each said valve to regulate the flow rate.
3. A device for monitoring the flow rate through at least one valve
to enable each said valve to be converted effectively into a
flowmeter, said device comprising a transducer connected to each
said valve for providing a first signal representative of the
position of the valve member of each said valve, electronic
processing means which receives said first signal and having means
enabling input of further signals representing static initial
conditions and variable operating conditions influencing the flow
rate, wherein said electronic processing means includes means
enabling storage of data relating to the flow characteristic curves
of a plurality of different types of valves, whereby said
electronic processing means calculates the flow rate through each
said valve from (a) said first signal, (b) the flow characteristics
of said valve and (c) said further signals, said device further
comprising display means connected to the output of said electronic
processing means for displaying said calculated flow rate and
control means connected to the output of said electronic processing
means for adjusting each said valve to regulate the flow rate.
4. A device as claimed in claim 2 or 3, in which said control means
activates a servo-mechanism connected to said valve to regulate the
flow rate through said valve in accordance with programmed
instructions and prevailing operating conditions.
5. A device as claimed in claim 1, 2 or 3, in which the electronic
processing means monitors and controls up to 250 valves
simultaneously in accordance with prescribed conditions.
6. A device as claimed in claim 1, 2 or 3, wherein the electronic
processing means actuates an alarm if the flow rate ascertained
falls outside a predetermined range of acceptable flow rate.
7. A device as claimed in claim 1, 2 or 3, wherein the electronic
processing means predicts the effect of variations in temperature,
pressure and valve opening on the flow rate.
8. A device as claimed in claim 1, 2 or 3, in which the transducer
is connected to the electronic processing means via an
analog-to-digital converter for converting the output of the
transducer into digital form for input into the electronic
processing means.
9. A device as claimed in claim 1, 2 or 3, wherein said electronic
processing means is a microprocessor having storage means
associated therewith containing data relating to the flow
characteristics of a plurality of different types of valves and
data regarding the effect of viscosity variations on flow rate and
data relating to the variations in viscosity with temperature for a
plurality of different fluids.
10. A device as claimed in claim 9, in which the transducer is
connected to the electronic processing means via an
analog-to-digital converter for converting the output of the
transducer into digital form for input into the electronic
processing means.
11. A device as claimed in claim 9, further comprising a key-board
for enabling input of the static initial conditions to the
microprocessor.
12. A device as claimed in claim 9, in which the variable operating
conditions are supplied to the microprocessor from temperature and
pressure sensors, and wherein calibration data is supplied to the
microprocessor from flow meters.
Description
TECHNICAL FIELD
The present invention relates to a device for ascertaining the flow
rate through at least one valve, which is capable of continuously
monitoring and controlling the flow rate through several valves
simultaneously.
BACKGROUND OF THE INVENTION
At present, a range of mechanical, magnetic and electronic switches
may be provided on or attachable to valves to provide an indication
as to when a valve is fully open or fully closed, however, it has
not been possible to accurately indicate intermediate positions of
the valve stroke in a simple and economical way.
For instance, different types of valve have different flow
characteristic curves relating percentage flow through the valve
against percentage opening of the valve, so that even if the
percentage opening of several different types of valve was the
same, then widely differing flow rates result and thus make it
extremely difficult for simple mechanical, magnetic and electronic
devices, which measure the actual opening of the valve, to give a
precise indication of the flow rate through the valve.
Further, for a given pressure and valve opening, changes in the
temperature and viscosity of the fluid alter the flow performance
which is difficult to compensate for with simple arrangements, and
with very viscous fluids, if the temperature drops below a certain
critical point, then viscosity may increase to an extent at which
flow will cease altogether.
The aim of the present invention it to provide a device capable of
ascertaining flow rate through at least one valve simultaneously
and displaying said flow rate or utilising said flow rate to
control said at least one valve.
DISCLOSURE OF THE INVENTION
According to the present invention a device for ascertaining flow
rate through at least one valve comprises a transducer connectable
to said at least one valve to be monitored, for providing a first
signal representative of the position of the valve member of said
at least one valve, electronic processing means receiving said
first signal and having means enabling input of the information
and/or further signals representing factors influencing the flow
rate, said electronic processing means being capable of calculating
flow rate through said at least one valve from said first signal
and said input information and/or said further signals, the output
of said electronic processing means being connected to a display
means for displaying said calculated flow rate and/or to control
means for adjusting said at least one valve to regulate the flow
rate.
Preferably, the electronic processing means comprises a
microprocessor programmed to calculate the flow rate through said
at least one valve from equations representing the characteristic
curve of said at least one valve which are stored in read-only
memory (ROM) associated with the microprocessor. The various
factors influencing the flow rate include the pressure drop across
said at least one valve and the temperature of the fluid and these
may be input to the microprocessor either via a keyboard or diectly
from respective pressure and temperature sensing devices. A further
factor influencing the flow rate is the viscosity of the fluid and
information regarding the viscosity is input to the microprocessor
via the keyboard as an initial condition when setting up. The input
information can be displayed on the display means for an operator
to check its accuracy prior to input of the information to the
microprocessor to minimise the possibility of errors and
additionally, with direct input of information relating to
temperature and pressure, information regarding these values can be
supplied by the microprocessor to the display to enable an operator
to check that the temperature and pressure are at the required
levels.
Since viscosity of the fluid varies with temperature, data
regarding this variation for each type of fluid to be monitored is
also stored in read-only memory associated with the microprocessor
to enable the microprocessor to compensate for changes in viscosity
due to variations in temperature.
The output of the microprocessor may additionally or alternatively
be connected to means for controlling the position of the valve
member of said at least one valve being monitored to enable the
flow rate to be regulated or maintained, within prescribed
tolerance levels from a desired value, independently of changes in
pressure or temperature and/or to annunciate an alarm, if
operational conditions cannot be maintained within prescribed
tolerance levels.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described further, by way of
example, with reference to the accompanying drawings, in which:
FIGS. 1a, 1b, 1c and 1d illustrate typical flow characteristics of
four different types of valve;
FIG. 2 is a series of graphs illustrating variations in viscosity
of various fluids with respect to temperature;
FIG. 3 is a graph illustrating the relationship between the
viscosity and percentage change in flow rate at a constant pressure
drop;
FIG. 4 is a block diagram of the device according to the present
invention; and
FIGS. 5a and 5b illustrate examples of linear and rotary position
transducers.
DETAILED DESCRIPTION
Referring to the graphs shown in FIGS. 1a, 1b, 1c and 1d, typical
flow characteristic curves are shown for four different types of
valves which clearly illustrate the variation between the flow
characteristics of different valves and other types of valves can
be treated in a similar way. The characteristic illustrated in FIG.
1a is for a Saunders Type "A" (Weir type) diaphragm valve and it
can be seen that, for a 50% opening of the valve, the percentage
flow through the valve would be of the order of approximately 65%
whereas for a different type of diaphragm valve, namely a Saunders
Type "KB" (straight through) diaphragm valve as illustrated in FIG.
1b, a similar percentage opening would give a percentage flow
through the valve of the order of 85%. For other types of valve,
such as a ball valve, the characteristic of which is illustrated in
FIG. 1c, and butterfly valve, a typical characteristic for which is
illustrated in FIG. 1d, a percentage opening of 50% would provide a
19% flow in the case of the butterfly valve and a 35% flow in the
case of a ball valve. Consequently, the difficulties involved in
providing a direct readout of the flow rate through a valve
determined from the degree of opening of the valve can be clearly
seen, in that it is a difficult matter to accommodate for such
widely varying flow characteristics of different types of
valves.
In consequence, different techniques have so far only sought to
indicate whether the valve was open or closed and the flow rate
through the valve was hitherto determined using flowmeters.
Apart from variations in flow characteristics for different valve
constructions, the flow rate through a valve is determined by the
viscosity of the fluid flowing through the valve and since
viscosity varies with temperature, then the temperature of the
fluid also has an effect on the flow rate, which introduces an
additional variable which is again difficult to compensate for when
attempting to provide an accurate indication of the flow rate
through a valve. Typical viscosity/temperature curves are
illustrated in FIG. 2 for nine different types of fluid of varying
viscosity as listed in the Table below:
______________________________________ TYPICAL VISCOSITY TEMP
CURVES CURVE FLUID S.G. ______________________________________ 1
GAS OIL 0.85 2 HEAVY DIESEL FUEL 0.88 3 100 SEC FUEL OIL 4 BRITOLUM
0.93 5 400 SEC FUEL OIL 0.95 6 900 SEC FUEL OIL 0.95 7 1400 SEC
FUEL OIL 0.95 8 3500 SEC FUEL OIL 0.975 9 BUNKER "C" 0.99
______________________________________
A further graph, illustrated in FIG. 3, illustrates the
relationship between viscosity and percentage change in flow rate
at constant pressure drop which can be assumed to be valid for all
valve types, and which illustrates the direct viscosity has on flow
rate.
In the device of the present invention, as illustrated in FIG. 4, a
position transducer 10, which may be a rotary or a linear position
transducer, is connected to a valve so that it is displaced with
the valve actuator member, opening and closing the valve, so as to
measure the valve stroke and to produce an electrical signal
determined by the position of the valve actuator member. A suitable
transducer would be an analogue potentiometric division transducer
and linear transducers are known having strokes of between 2.5
meters and 250 mm and a suitable transducer would be selected
according to the stroke of the valve to be monitored. As an
alternative to a linear transducer, for valves utilising a rotary
movement of the valve member rather than a linear displacement, a
rotary transducer would be utilised, also in the form of a
potentiometer the wiper of which is attached to the spindle of the
valve member.
Examples of suitable arrangements of transducers are illustrated in
FIGS. 5a and 5b, 5a being a schematic illustration of a rotary type
transducer and 5b illustrating a linear transducer. In each case
the transducer T is potentiometer the wiper of which is
displaceable with the valve actuator member of the valve to which
it is connected, and two potentiometers A and B are provided to
allow adjustment of the circuit to accommodate different
transducers. A temperature stable resistance and Zener diode
network is provided to maintain stable potentials at the ends of
the transducer, and the output voltage of the transducer T is
buffered with a voltage follower to enable processor circuitry to
be placed remotely from the valve up to a distance of 200 meters.
The output of the voltage follower is supplied as an input to the
analog-to-digital converter 12 of FIG. 4. The analog-to-digital
converter 12 converts the transducer output voltage to a digital
signal for input to a microprocessor 13. The output of the
analog-to-digital converter 12 are supplied to the microprocessor
13 via a peripheral random access memory (RAM) and input-output
device 15, the output data lines 14 of the analog-to-digital
converter 12 being connected to a port A of the input-output device
15 and then provided as an input to the microprocessor 13 via data
bus 16. Control of the analog-to-digital converter 12 is performed
by the microprocessor 13 by means of control lines 17 and 18.
The peripheral RAM and input-output device 15 has two further
ports, port B and port C for driving the display 19 under the
control of the microprocessor 13. Input of initial conditions
governing the flow rate are provided by means of a key-pad 20 which
enables an operator to identify to the processor the particular
fluid flowing through a valve being monitored, to specify the type
of valve and to input information such as the temperature and
pressure of the fluid. Detailed information regarding the flow
characteristics of the different types of valves to be monitored,
together with information regarding the viscosity/temperature
curves and the effect viscosity has on flow rate, such as
illustrated in graphic form in FIGS. 1 to 3 are stored as data in
the program memory 21 which also contains the controlling program
for the microprocessor 13. The program memory 21 is suitably
Erasable Programmable Read-Only Memory (EPROM) so that if
necessary, the contents of the memory can be erased and a new
program incorporated for the characteristics of a different family
of valves or fluids.
As an alternative to inputting information regarding the pressure
and temperature via the keyboard, appropriate means may be provided
for inputting such information directly into the processor system
from temperature probes 23 and pressure gauges 24, or even from
flowmeters 25 for comparison purposes. Further, the microprocessor
can be provided with suitable output control means 22 operating a
servo-mechanism for automatically adjusting the valve to regulate
the flow rate within prescribed tolerance limits, so as to enable
the flow rate to be maintained independently of variations in
pressure or temperature. Further, the microprocessor could
annunciate an alarm if prescribed tolerance levels could not be
maintained, or actuate other systems regulating the temperature and
pressure of the fluid in a pipeline.
The use of a microprocessor enables a large number of valves to be
monitored simultaneously and an indication to be given of fluid
flow through each valve for any number of fluid types including
water at a specified temperature, preferably in the range 0.degree.
to 250.degree. F., (-18.degree. to 120.degree. C.), and for the
particular valve actuator position to be expressed as a percentage
of the flow of water at 0.degree. F. (-18.degree. C.) through the
same valve when fully open. The arrangement of the present
invention may be a single integrated unit monitoring up to 250
valves simultaneously or it may be combined with a mini-computer
with a visual display unit (VDU), or a main-frame computer and the
output can be provided via the computer if required.
In operation, the microprocessor 13 performs a series of
calculations utilising the input data supplied via the keyboard or
directly from in-line sensors, together with the information
provided by the position transducer of the valve, and data stored
in the memory 21 relating to the flow characteristic curves of each
valve and the flow characteristics of the fluid flowing through the
valve, to provide an output which is an indication of the flow rate
through the valve derived directly from the position of the valve
member. It is also possible to utilise the same information to
ascertain the effect that variations of temperature or pressure
will have on the flow through the valve.
Thus, a device has been provided which enables a plurality of
valves to be simultaneously monitored and for the flow rate through
valves to be ascertained in dependance upon the actual opening of
the valve, and whilst the preferred embodiment relates particularly
to valves, it should be readily apparent to a person skilled in the
art that the device of the present invention is equally applicable
with minor modification, relating to the type of transducer used,
to pumps, for monitoring the flow therethrough.
* * * * *